Full Wave Rectifier

Ungapped rings to bind them all /

This is an example of a cheap, compact, full wave AC to DC rectifier. All of the components were ordered from Radio Shack. The PC board was trimmed with a Dremel cut-off tool after soldering. Shrink tubing or electrical tape can be used to protect it before use. The diode group in the upper right of the second pic is a better theoretical example of a 4 diode rectifier circuit. The array is compacted for the real one.

15vac input equals 12vdc output. All conversions have a loss factor.

Inputs: AC goes to the 2 Yellow leads.

Outputs: Red is DC+ and Black is DC-.

Best results can be achieved by floating the output of an AC coil to the 2 Yellow leads, then feeding the DC output to the battery or other DC components in a closed circuit. Otherwise, it can be used inline ahead of DC components in a mixed AC/DC set-up with a common ground. A Trail Tech or other AC regulator can be used on the AC side to limit max voltage.

A capacitor can be added across the AC input to smooth the AC pulse.

Search "full wave rectifier" online to provide further explanation and orientation of the diodes if you can't see what's going on in the pics. Basically all 4 have the silver stripe toward the DC+ (Red) output.

BTW: Using just a single diode in line for half wave rectification results in a 12vac to 5vdc output.(edited)

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Re: Full Wave Rectifier

Ungapped rings to bind them all /
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Re: Full Wave Rectifier

1N4004? 1A max, please dont run lights or anything else off it!

Re: Full Wave Rectifier

Ungapped rings to bind them all /

Puch is running DC for led tail light, 1156 headlight and 1 amp led cob high beam. No prob. All DC grounds have to go to DC rectifier. Puch horn button contact needs to be insulated with tape or replaced. It grounds out the dc system. Been running a hobbit with same setup for 2 years with a 35w fog lamp headlight.

Re: Full Wave Rectifier

Francois Labat /

Hey Local Hobbituary,

How do you determine the output of your electrical system?

I got the motobecane CDI le partie. I know I'll get 12V but is there a way to determine the maximum load? I'm looking for a front "halo" looking light but unsure whether I'll be able to power it.

Thanks

Re: Full Wave Rectifier

Ungapped rings to bind them all /

Your accessory should list the watts or amps it needs at 12vdc.

Volts x amps = watts.

Watts / volts = amps

A 10w bulb at 12vdc = 10w/12v = .83a or requires 0.83amps@12vdc.

That same 10w bulb at 6vdc = 10w/6v = 1.6 amps for the same brightness.

In mopeds, lights just get dimmer at idle (+/- 4v) and brighter at wot (12-18v) with the changing rpms.

To answer your question, add up the watts or amps of all your lights and accessories then calculate if the coil is rated for the total wattage required at a nominal voltage of 6 or 12v with everything "on" ( or use an ammeter to measure real amp draw..). Coils are usually rated in Watts. Owner's manual or Wiki or someone here might know yours.

LEDS require regulated DC voltage to survive in most cases.. Don't think you can test or run them on the raw AC output of your coil unless they have protective circuitry built in. Most will get hammered to death immediately.

Always regulate the AC output of your coil(s) first to eliminate destructive high voltages, then rectify to DC if needed for leds, aux port or other DC accessories (excluding the ignition), ... then add a battery if you want steady DC voltage for accessories & lights at all rpms.(edited)

Re: Full Wave Rectifier

Francois Labat /

Good explanation thanks.

I have to determine what power rating the "Motobecane CDI Le Partie" coil has.

Yeah, I'm looking into a rectifier and voltage regulator. I seen the expensive trail tech one on treats. I wonder if it has a capacitor in there. I know having a cap will allow u to have a more consistent output.

Thanks

Re: Full Wave Rectifier

the trailtech one is real nice. I think you can do the same much more cheaply but it's a good piece.

How's this holding up with miles?

Re: Full Wave Rectifier

Brad William /

Do you need DC on a moped?

Horn likes AC, incandescent ffilaments are happy with AC, 12v LEDs that like ac are all over the web. They all have internal rectification and are dirt cheap.(edited)

Re: Full Wave Rectifier

Brad William /

Re: Full Wave Rectifier

Emil Kniemel /

I'm actually surprised RadioShack is still around, good for them!

Re: Full Wave Rectifier

Dirty30 Dillon /

> Brad William Wrote:

> -------------------------------------------------------

> Do you need DC on a moped?

>

> Horn likes AC, incandescent ffilaments are happy with AC, 12v LEDs

> that like ac are all over the web. They all have internal rectification

> and are dirt cheap.

Horns are simple diaphragms, so they don't care. Of course incandescent likes it just fine as well.

12VDC Led's that can function with 12VAC are available, but the longevity is not that great. The internal rectifiers typically add more heat into an already fragile housing/cooling situation, let along the fact that most LED failures I see on bikes are board level heat issues.

In addition, running a Reg/Rec allow a battery to be used for steady lighting, and the ability to run things like water pumps and aftermarket gauges.

Re: Full Wave Rectifier

Question, if I'm just running a single LED auxiliary light as my high beams and I want to rectify it using this method; do I wire the rectifier in before or after the switch I'm using?

Does it even matter?

I'm using this switch with this light. I'm currently taking a line off of my lighting coil to hit one of the leads on the switch and taking the other lead to the positive on the light. I've grounded the other lead off of the light to forks.

At the moment, I'm running it off AC power and and everything is working fine. It's plenty bright and stays steady even at idle. I haven't fried anything yet but that's probably due to me running voltage regulator on my bike.

I'd like to avoid frying it anytime in the near future so I need to rectify it somehow before that happens. I had been considering buying the trail tech rectifier mentioned above and converting my whole system to LED bulbs.

Doing this seems much more cost effective though and all my other lights are working just fine so no need to fix what's not broken.

So what's the best way to go about using one of these little guys with my light and switch combo?

Re: Full Wave Rectifier

Ungapped rings to bind them all /

Been rock solid over hundreds of miles on several bikes.

I tried "protected" LEDs on AC, but mine always died on long rides/speed runs. .. but post 'em if yours work!

Starting with an AC regulator is definitely the best thing to do. It will eliminate most or all of your blown bulb problems. The trail tech is proven.

DC just gives you a more stable option for experimenting with LEDs and other DC accessories. I haven't had anything fail on a regulated, fully rectified DC bike and the lights are motorcycle bright.

Doesn't matter where you use the rectifier it if its hooked up right. You can convert the entire bike or just the headlight. Full wave is better then half wave. Less pulsing with more available voltage/current..

AC oscillates or alternates direction.. think of it as a saw blade going back and forth... which means that is does not have polarity or a pos & neg like DC.

DC is more like a water faucet and a drain.

The 2 yellow wires of the rectifier connect to the output of the AC coil whether its 2 wires or a single output wire and chassis ground. The Red+ and Black- wires of the rectifier represent the positive and negative connections for the DC side. Its best to isolate or float the DC circuit. A common AC/DC ground can mess with the rectified DC output (cancellation/pulsing).

LEDs have polarity. So with your headlight, the AC supply to the light would connect to one yellow wire on the rectifier and the other yellow would go to the common or chassis ground, then the red wire would go to the + connection of the light and the black wire would connect to the bulb ground. The rectifier can be inserted before or after the switch. You could easily have an AC, OEM low beam/driving light and a rectified DC aux LED high beam for night riding if ya like. I use a separate on/off switch for the aux LED head light..

Re: Full Wave Rectifier

> Local Hobbituary Wrote:

> -------------------------------------------------------

> The rectifier can be inserted before or after the switch.

> You could easily have an AC, OEM low beam/driving light and a rectified

> DC aux LED high beam for night riding if ya like. I use a separate

> on/off switch for the aux LED head light..

This is how it's currently set up minus the rectifier. My headlight and taillight are wired straight off the regulator and always on. The aux LED fixture is wired through a switch so i can turn it on at night when it's needed.

So if I'm understanding the last post correctly, I can take one yellow wire off the rectifier to hot lead coming off of my regulator and the other can be grounded to the chassis. Then I could take the red wire off the rectifier to one lead of my switch and connect the other to positive lead on my LED lamp. Then the black wire off the rectifier could go to the negative lead on the LED lamp.

In your original post you said you connected both yellow wires off the rectifier to one lead coming off of your lighting coil. So do I do that or ground one to the chassis?

The aux LED fixture is the only thing I'm trying to rectify.

Re: Full Wave Rectifier

Ungapped rings to bind them all /

You are 100% correct for your application. Rectifying at the light coil would be for full bike DC conversion. In that case the second yellow wire connection for the rectifier would be either a second wire from an isolated coil or to a common chassis ground like you said. There are a couple of errors in that first post.. but ya can't edit or delete to correct on MA after a few minutes...

Re: Full Wave Rectifier

Francois Labat /

> Local Hobbituary Wrote:

> -------------------------------------------------------

> You are 100% correct for your application. Rectifying at the light coil

> would be for full bike DC conversion. In that case the second yellow

> wire connection for the rectifier would be either a second wire from an

> isolated coil or to a common chassis ground like you said. There are a

> couple of errors in that first post.. but ya can't edit or delete to

> correct on MA after a few minutes...

Sounds like you know what you're talking about. I've been figuring all this out.

Check out my post and comment if you disagree with what I've been rambling on about.

BTW the major inconvenience I find with the trail tech is having to run a battery or 2 big ass capacitors... I really don't like that.

https://www.mopedarmy.com/forums/read.php?6,4277720(edited)

Re: Full Wave Rectifier

Ungapped rings to bind them all /

Yeah...many of the combo reg/rec units take more of a flaccid Windows or condom approach, trying to accomodate everything while compromising all. I'm guessing from the output of the Trail Tech AC regulator that it basically clips the AC sine wave in both directions at the reference voltage you select with the adjustable pot. It doesn't appear to do anything to boost or regulate low voltage, which can involve other chicanery that costs both current and voltage. The TT AC regulator plus basic "Black Diamond" full wave rectifier is more of a DOS approach that does exactly what's needed and nothing else: 1. Limit upper voltage at "x" 2. Convert remaining AC voltage to DC where needed. The result is still an unrefined electrical mess, but it reliably puts out the maximum safe amount of electrifying voltage and amped up satisfaction with adequate protection for your mopeding pleasure.

Re: Full Wave Rectifier

So any chance you could post a link to the electrical components you used for the rectifier you made in the OP? I know you said they came from radioshack, but it's hard to tell from the pic the actual part numbers. I'm definitely wanting to give this a shot for the light I mentioned above, I just need some direction as to what I should buy.

Also you said in one of the posts 15VAC becomes 12VDC after rectifying using this method. Since my regulator outputs 12VAC and the specs for my light say its designed to work on 12-24 Volt systems, how do I go about keeping it 12V after rectifying?

Would it be better to bypass my regulator from the light coil just for the switch and light combo I'm using and keep everything else running off of the regulator?

For the record my aux LED "high beam" uses 20 W at 12VDC and my other three lights pull about 15W total at 12VAC. My coil is good for 80W.

Once I have my brake light switches working properly my tail lights will pull an additional 36 W but only while I'm braking.

Re: Full Wave Rectifier

Blaine- The artist formerly known as Plumber Crack "(OFMC)" /

A dedicated full wave rectifier doesn’t require soldering or breadboard, costs like $2 and can handle far more current.

You can buy scooter rectifiers that have cool looking heat sink fins and a mounting hole for $6.

Re: Full Wave Rectifier

Ungapped rings to bind them all /

Sure, take the easy way out...... even with a mounting hole and cool fins they're not as much fun as building you own stuff... :P Looks like Radio Shack is slowly running out of stock and is over-pricing everything now, including these IN4001s. ($2.00 vs 0.19 elsewhere!) There are a ton of suppliers. Pay attention to surge Amps, general ratings and reverse voltage/reverse current. Most will wildly exceed moped requirements. You want to avoid the 12v Zener diodes, which break down at 12v vs being rated to work at 12v and will fry in this application. I run the AC regulator at 15v which is probably fine whether you rectify or not. Please post any improvements or refinement you come up with. I originally salvaged a bunch of diodes and electrolytic caps to play with from CRT TV chassis before recycling the rest....(edited)

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